In metal cutting

Built-up Edge. At relatively low speeds in metal-cutting operations, the tool tip does not get hot enough for crater wear to be significant. Under these conditions the metal may, however, become welded to the tool tip as built-up edge (Fig. 2c). 

Garbonitrides. Use of carbonitrides in metal cutting tools, both Ti(C,N) coatings (18) and Ni—Mo cemented carbonitrides (19), is expected to increase in the 1990s. 

The main function of most lubricants is to reduce friction and wear between moving surfaces and to abstract heat. They also have to remove debris from the contact area, e.g. combustion products in an engine cylinder, swarf in metal-cutting operations. Sometimes they have to protect the lubricated or adjacent parts against corrosion, but this is not a prime function of most lubricants. On the other hand, many lubricants do contain corrosion inhibitors and some lubricating oils, greases, mineral fluids and compounds are specially formulated to prevent the corrosion of machinery or machine parts, particularly when these components are in storage or transit. These temporary protectives are described in Section 17.3. 

Hardness is measured by the Rockwell A-scale diamond cone indentation test (HRA) or by the Vickers diamond pyramid indentation test (HV). Although the Rockwell scale has been used for decades in the carbide industry as a measure of hardness, a true indication of the resistance of the tool to deformation in metal-cutting operations can be obtained only by measuring hardness at elevated temperatures. The hardness of cemented carbides decreases monotonically with increasing temperatures. 

Aside from the primary function of friction and wear control, lubricating oils are often called on to serve other purposes, such as corrosion prevention, electrical insulation, power transmission and cooling. This last is particularly important in metal cutting and grinding. 

Organic disulfides and chloroorganic compounds in boundary lubrication conditions form iron sulfide (AHf = -1.04 eV), iron chloride (AHf = -3.54 eV), or iron bromide (AHf = -2.59 eV), which decrease wear and protect against seizure. Some chlorinated and brominated hydrocarbons in the presence of DBDS produce strong synergism in severe conditions involving lubrication in metal cutting (McCarroll et al., 1978 Mould at al., 1973 Plaza, 1989 Plaza et al., 1993 Sakuri etal., 1967). 

Trichloroethanef X Cleaning solvent for electrical equipment, motors, electronic instruments and upholstery solvent for adhesives, coatings and textile dyes coolant and lubricant in metal cutting oils component of inks and drain cleaners... 

There are potential quality assurance problems with the analysis of PCAs at trace levels in environmental samples because of their use in some consumer products like PVC or paints, and in metal cutting oils. Standard precautions used for the analysis of PCBs and other organochlorines such as use of glass distilled solvents, high temperature heating of filters, glassware, and sodium sulfate, and minimal use of plastics, should also minimize contamination by PCAs. This contamination is potentially more difficult to control under field conditions where PCAs maybe incorporated into outdoor paints and sealants or may be residues on or in sampling equipment. 

To illustrate, suppose a company wishes to anticipate a patent on a composition used in metal cutting, this composition containing certain fatty acids. The literature reveals no pertinent statement prior to the date in question. The searcher who has not established a viewpoint will turn in a negative result. 

To explain the pronounced effect of additives on tool wear in metal cutting, Dorinson [74] developed a theory of the inhibition of junction growth at contacting asperities based on the concept of dynamic competition between asperity adhesion and the quenching of such adhesion by additive reaction. The adhesion mechanism involves the following sequence migration of metal on the chip side of the contact interface to the tool side,... 

The dynamic thermocouple, also known as the "Herbert-Gottwein" thermocouple, measures the temperature at the rubbing interface of two dissimilar metals by making it the hot junction of a thermoelectric circuit. The utilization of this principle for the measurement of the chip-tool rubbing temperature in metal cutting appeared on the scene in 1925/1926 [6, 7, 8] and for the measurement of temperature in ordinary rubbing about 10 years later [9]. 

Figure 15-6. Comparison of observed and calculated temperatures for the chip-tool interface in metal cutting. From data by Loewen and Shaw [13] for sintered carbide cutting AISI B1113 steel.

Several researchers tried to replace the single-shear plane model by a shear zone model. Lee and Shaffer (1951) provided a slip-line solution by applying the theory of plasticity. In the slip-line model, the metal is assumed to flow along the line of maximum shear lines. The slip-line field solution cannot be applied easily to three-dimensional as well as strain-hardening cases. Sidjanin and Kovac (1997) applied the concept of fracture mechanics in chip formation process. Atkins (2003) demonstrated that the work for creation of new surfaces in metal cutting is significant. He also points out that Shaw (1954) has shown this work to be insignificant. However, when this work is included based on the modem ductile fracture mechanics, even the Merchant analysis provides reasonable results. 

Shaw, M. C., Finnic, I. (1955). The shear stress in metal cutting. Transactions ofASME, 77, 115-125. 

A variety of other ternary and quaternary carbides and carhonitrides is especially interesting for use in metal cutting tools in the form of layers, and powder particles have been investigated recently for their specific heat, temperature and thermal conductivity [66]. The behavior of the heat conductivity of most of these compounds is similar to that of the group IVB carhonitrides for (near) stoichiometric composition showing a positive curvature of heat conductivity as a function of temperature. Interestingly, however, Nb- and Mo-containing ternary titanium carbides and nitrides and quaternary titanium carhonitrides show a hnear behavior in the same temperature interval. 

In most applications WC-Co is subjected to temperatures which can be as high as 900-1000°C (as in metal cutting). Therefore knowledge of the effect of temperature on hardness is essential for a correct selection of the grades suitable for a specific application. 

Machine tool vibrations Self-excited vibrations in metal cutting... 

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